VALID 06Z SAT 19/10 - 06Z SUN 20/10 2002
ISSUED: 18/10 22:46Z
FORECASTER: DAHL/ GATZEN

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS S ADRIATIC SEA INTO THE S BALKAN STATES

GENERAL THUNDERSTORMS ARE FORECAST ACROSS N MEDITERRANEAN REGIONS

GENERAL THUNDERSTORMS ARE FORECAST ACROSS S/ W SCANDINAVIA, NORTH-, BALTIC SEA, BENELUX, AND N- GERMANY

SYNOPSIS

IMPRESSIVELY LARGE AND INTENSE UPPER LONGWAVE TROUGH WILL EXTEND FROM THE NORTHERN ATLANTIC ACROSS CNTRL EUROPE INTO THE CNTRL MEDITERRANEAN REGIONS. VORT MAX ATTM AFFECTING FRANCE---IS MIGRATING AROUND THE BASE OF THE MAIN TROUGH---AND WILL AFFECT THE CNTRL AND EASTERN MEDITERRANEAN DURING THE DAY. EAA REGIME OF INTENSE SFC LOW---ASSOCIATED WITH EX-KYLE---ATTM OVER THE E ATLANTIC...WILL AFFECT THE IBERIAN PENINSULA AND THE GULF OF BISKAY TOWARDS THE END OF THE PERIOD. OTHERWISE...DEEP POLAR/ARCTIC AIRMASSES DOMINATING MUCH OF THE FORCAST AREA. (DAHL)

DISCUSSION

...MEDITERRANEANMEDITERRANEAN MEDITERRANEAN ...
PLUME OF WARM/MOIST AIRMASS IS EXTENDING ACROSS THE S ADRIATIC SEA INTO THE S BALKAN STATES. THIS PLUME IS EXPECTED TO REACH THE AEGEAN SEA DURING SATURDAY. SOUNDINGS INDICATE A HUGE CAP AND VERY SHALLOW BOUNDARY-LAYER MOISTURE WITHIN THIS PLUME... YIELDING MARGINAL MLCAPE VALUES. AS VORT MAX APPROACHES... VIGOROUS FORCING FOR UPWARD MOTION IS EXPECTED...WHICH SHOULD ALLOW AT LEAST ISOLATED TSTMS TO FORM DESPITE THE LARGE CAP. ANY TSTM THAT FORMS...WILL POSE THE THREAT OF DAMAGING WIND GUSTS AS 0-7 KM SHEAR MAY WELL APPROAC 100+ KNOTS. ALSO... DRY ENVIRONMENT SHOULD YIELD STRONG NEGATIVE BUOYANCY OF THE DOWNDRAFTS. ALSO...SOME HAIL SHOULD BE EXPECTED. GIVEN INTENSE SHEAR... SPLITTING STORMS MAY DEVELOP... ALSO... OROGRAPHY/OTHER INFLUENCES MAY RATHER EASILY MODIFY LOW-LEVEL WIND REGIME SUCH THAT A HELICAL INFLOW IN GENERATED. IF SO... AN ISOLATED TORNADO MAY OCCUR AS WELL ESPECIALLY LATE IN THE DAY AS LCL HEIGHTS WILL BE VERY LOW. IN THE DEEP POLAR/ARCTIC AIRMASS SPREADING ACROSS THE N MEDITERRANEAN REGIONS...NUMROUS SHOWERS AND TSTMS ASSOCIATED WITH DEEP CONVECTIVE MIXING ARE ANTICIPATED. GIVEN QUITE IMPRESSIVE SHEAR MAGNITUDES... THREAT EXISTS A FEW DAMAGING WIND EVENTS. LIMITING FACTOR MAY BE LOW- LEVEL CAA WHICH SHOULD LIMIT DEPTH OF CONVECTIVE MIXING... AND THUS INHIBIT EFFECTIVE VERTICAL MOMENTUM TRANSFER. AN UPGRADE WILL BE NEEDED IF CONVECTION TURNS OUT TO BE DEEPER THAN EXPECTED ATTM. (DAHL)

...S/ W SCANDINAVIA, E NORTHSEA, BALTIC SEA, BENELUX AND N GERMANY...
COLD AIRMASS FLOATING EASTWARD ... T 500 REACHES -35° C OVER S SCANDINAVIA. SOME VORT- MAX WILL INFLUENCE S SCANDINAVIA ASSOTIATED WITH CYCLONAL VORTICITY ADVECTION. ESPECIALLY ABOVE WARM WATER SURFACES OF NORTH- AND BALTIC SEA WIDESPREAD SHOWERS WILL FORM ... AND TSTMS ARE LIKELY, PROPAGATING EASTWARD INTO BENELUX/ N GERMANY. LOW LEVEL SHEAR WILL BE BIG ENOUGH TO ORGANISE SOME OF THESE STORMS, AND SOFT HAIL, STRONG WIND GUST AND SOME WATERSPOUTS SHOULD BE POSSIBLE. WIND GUSTS UP TO 50 KN SHOULD BE THE MAIN THREAT. SEVERE POTENTIAL SEEMS TO BE TOO SMALL TO WARRANT A SLIGHT RISK THOUGH. (GATZEN)

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